聚乳酸為現今綠色塑膠之代名詞，且於市面之產品應用也愈漸廣泛。以產品生命週期評估，進一步了解產品各種環境衝擊及綠色訴求，將是產品應用的重點。個案研究以生命週期評估、碳足跡、毒性評估及生態效益等方法，探討聚乳酸廢棄物之生命週期環境衝擊。研究結果主要包含四大部分，第一部分為聚乳酸之生命週期評估；第二部分為不同回收處理方式之生命週期評估比較；第三部分為聚乳酸與傳統塑膠之碳足跡與毒性比較；第四部分為聚乳酸與傳統塑膠之碳足跡與生態效益比較。結果顯示：(1)聚乳酸之生命週期評估，於肥料、農藥及運輸之原料種植階段其總碳足跡為3.92 KgCO2-eq；於製造階段為2.66KgCO2-eq；(2)不同回收方式處理聚乳酸廢棄物，以仿塑木複合材方式碳足跡0.01 KgCO2-eq.最優，而以鹼性水解回收方式碳足跡8.67 KgCO2-eq.最高；(3)不同回收比例結合焚化或掩埋，比較新產品摻配回收料結果，以回收率100%之酸性水解回收結合焚化處理方式之碳足跡3.21 KgCO2-eq.優於鹼性水解回收結合焚化處理方式8.67 KgCO2-eq.；(4)聚乳酸與傳統塑膠之碳足跡比較，以PET之總碳足跡排放量為低6.46 KgCO2-eq.，而以PLA鹼性水解回收之總碳足跡排放15.25 KgCO2-eq.最高；聚乳酸與傳統塑膠之回收生態效益比較，以PET生態效益1667.47 NT/KgCO2-eq.最高，以PLA鹼性水解生態效益147.60 NT/Kg CO2-eq.價值最低。 Polylactic acid (PLA) is believed to be an green plastic, and is widely applied the products. For more realization PLA about the environmental issues by Life Cycle Assessment(LCA), this study focused on the environmental impact issues, carbon footprint, ecological toxicity assessment and eco-efficiency analyses for the PLA case study. The results contain with four parts, the first part is life cycle assessment of polylactic acid; The second parts is concering with the comparisions among the different recycling models by life cycle assessment; The third parts is the carbon footprint and toxicity among PLA and traditional plastics; The last parts, the ecoefficiency comparisions of polylactic acid and traditional plastics.The results showed that：(1) The carbon footprint is 3.92 KgCO2-eq of the polylactic acid that came from the fertilizers, pesticides and transportation emissions during the planting phase, the manufacture phase is 2.66 KgCO2-eq.；(2) For the different recycling models for PLA, the wood composite mode is 0.01 KgCO2-eq, and the alkaline hydrolysis model is worst in the value of 8.67 KgCO2-eq.；(3) the recycle PLA is more friendly carbon footprint with the acidic hydrolysis treatment(3.21 KgCO2-eq.) than alkaline hydrolysis(8.67 KgCO2-eq.), that combining with the incineration treatment；(4) Polylactic acid compared to the traditional plastics, PET carbon footprint is the low with 6.46 KgCO2-eq., and PLA alkaline hydrolysis model is the most with 15.25 KgCO2-eq; the PLA ecoefficiency is not significant, the PET is the high ecoeffieiency.
